TUESDAY, March 21, 2017 (HealthDay News) -- If you've got a family history of colon or rectal cancers, you probably need to start screening for these conditions before you turn 50, a cancer expert says.

People with a close relative who has had colon or rectal cancer have a greater risk of being diagnosed with these cancers too, said Dr. Walter Koltun, chief of colon and rectal surgery at the Penn State Health Hershey Medical Center in a hospital news release.

"A significant portion of the population does have those risk factors," Koltun said. "And their risk goes up significantly depending on who has been affected."

If more than one close relative has had colon or rectal cancer, your risk of getting such a cancer is 12 times greater, he added.

People who are diagnosed with colon or rectal cancers at a young age are more likely to have a genetic trait that could increase their risk for the disease. Doctors are still working to identify the exact genetic factors that trigger the diseases, Koltun noted.

Other factors that can up your risk of colon or rectal cancers include:

A family history of breast cancer, ovarian cancer or endometrial cancer.

Undergoing radiation for prostate cancer.

Having inflammatory bowel disease or colitis.

Having colon polyps.

A family history of colon polyps.

Colon and rectal cancers are usually considered diseases that affect older people. A recent study conducted by the American Cancer Society reveals a surprising increase in rates of these forms of cancer among young and middle-aged adults, Koltun pointed out.

"You should talk to your doctor sooner rather than later," Koltun recommended.

Genetic and environmental factors can play a role in the development of cancer. But Koltun cautioned that assessing family history for colon and rectal cancers and undergoing routine screening for these diseases based on known risk factors and current guidelines is important.